Nitro-based compounds and nitrate esters are primarily explosive materials used in the manufacture of explosive boosters, seismic boosters, military devices (such as anti-tank mines, anti-personnel mines, bombs, etc.) and other devices designed to be used as part of an ignition system. For example, nitro compounds and nitrate esters are commonly used to initiate a bore hole loaded with secondary explosives. Other applications include using nitro compound and nitrate esters to create seismic waves for exploration of gas and oil. Finally, some applications use nitro compounds and nitrate esters to act as a destructive mechanism, such as a bomb or a mine.
Typical nitro compounds and nitrate esters used in the aforementioned applications include non-limiting examples of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), octogen or cyclotetramethylene tetranitramine (HMX), cyclonite or cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), nitroglycerine, nitroglycol, and tetryl. These materials are commonly used on their own or in combination with each other. For example, a common combination used for seismic exploration is a TNT/PETN mixture called Pentolite. For some applications, these materials or combinations of materials are further combined with other non-explosive materials.
Some applications of Pentolite or other composition types (such as Composition B; a TNT/RDX mixture) are commonly used in boosters for seismic exploration. Explosive formulations intended for seismic exploration (e.g., that conducted for gas and petroleum exploration) have some particular characteristics since, on the one hand, they must maintain their explosive characteristics for at least 6 months from being placed in the subsoil, and, on the other hand, if they do not detonate, their explosive characteristics must disappear at the end of a determined time period so that they cannot be subsequently initiated or detonated due to an external stimulus, thus reducing the risk for the population of an accidental detonation. Seismic exploration is usually done under extremely harsh conditions, occasionally resulting in boosters failing to detonate due to priming system failure. As a result, undetonated explosive charges can remain buried in the soil or in the subsoil but containing potentially explosive compounds that can be accidentally detonated with the resulting risk for people and animals. Very often, the seismic exploration crew will not know whether a seismic booster has failed to detonate because of the type of blasting used. For example, the booster itself is typically buried deep enough and is small enough in its blasting effect that a surface disturbance cannot be used to determine effective detonation. The problem facing the land user is that a “live booster” will remain in the ground for many years. Most of the primary explosives used in “boosters” have a shelf life in excess of twenty years; thus, the latent risk for people is very high. Removal of undetonated boosters is very difficult, if not impossible and potentially a safety hazard.
Similarly, explosives used in military applications, such as bombs, grenades, etc. often do not function as intended and become latent hazards to civilian populations. Additionally, other devices such as mines are intended to have a long sleep time, which becomes a serious problem for the civilian population after intended use of the mine has expired.
Some methods and systems for the degradation or decomposition of undetonated explosive compositions have been developed. Some methods include the use of suitable microorganisms (bioremediation) to render nitro compounds and nitrate esters safe (see, for example, U.S. Pat. No. 7,240,618). The microorganisms are incorporated into the seismic boosters at the time of manufacture under the theory that the microorganisms will be activated after a certain period of time and consume the booster's explosive components (TNT, PETN, RDX, nitrocellulose, halocarbons and hydrocarbons). The method claims to render the seismic booster inert. However, methods of remediation utilizing microorganism show varying levels of effectiveness for the various types of explosive materials. Additionally, use of microorganisms in explosives remediation requires special preparation and culturing of the microorganisms which may be cost prohibitive in some countries.
Other methods for the degradation of undetonated explosive compositions are based on the use of enzymes capable of degrading nitroderivatives or nitroesters. In this sense, the capacity of several redox enzymes, such as ferredoxin NADP oxidoreductase, glutathione reductase, xanthine oxidase and oxyrase, to convert TNT into 4-hydroxylamino-2,6-dinitrotoluene (4-HADNT), as well as the capacity of the PETN reductase to degrade PETN (WO 97/03201) and TNT (WO 99/32636), are known. However, the use of enzymes is very delicate and presents the drawback that the enzymes can be inactivated if the conditions of the environment alter their shaping or secondary structure, they thereby lose their capacity to degrade said compounds.
Methods for the degradation of undetonated explosive compositions based on the use of chemical reagents for the degradation of said explosive compounds (chemical remediation), for example, the use of sodium chlorite to degrade RDX and HMX, have also been described; nevertheless, said methods require the dissolution of reagents and explosives to be degraded and, in addition, when the chemical reagent selected is very reactive with the explosive compounds (e.g., a chlorite), a composition that is unsafe both in its manufacture and in its use could be generated.
Thus, while various devices currently exist for remediating explosive materials, substantial challenges still exist. Accordingly, it would be an improvement in the art to augment or even replace current remediation systems or techniques with other systems and/or techniques. Effectively, although there are several methods and systems for reducing the risk of detonation of undetonated explosive charges, there is still a need to develop alternative methods and systems with respect to those existing which overcome all or some of the previously mentioned drawbacks. Advantageously, said methods and systems must enable, in addition to the decomposition of the undetonated explosive charge, the conversion of the explosive compounds into inert compounds and/or their degradation for the purpose of reducing or eliminating the environmental pollution caused by said compounds.